feat(dashboard): endpoint de download fișiere binare + tool epub-to-audio

- dashboard/handlers/files.py: handle_files_download() servește mp3/wav/zip
  din WORKSPACE_DIR cu Content-Disposition attachment, resolve dedicat
  (nu _resolve_sandboxed, care nu ajunge niciodată la WORKSPACE_DIR)
- dashboard/api.py: rutează /api/files/download
- tools/epub_to_audio.py: tool nou de conversie EPUB → audio
- cron/jobs.json, memory/kb/index.json: stare auto-generată (job runs,
  regenerare index KB)

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

dashboard/api.py

@@ -173,6 +173,8 @@ class TaskBoardHandler(
             self.handle_cron_status()
         elif self.path == '/api/habits':
             self.handle_habits_get()
+        elif self.path.startswith('/api/files/download'):
+            self.handle_files_download()
         elif self.path.startswith('/api/files'):
             self.handle_files_get()
         elif self.path.startswith('/api/diff'):